diff --git a/src/kernel/mgerror.rs b/src/kernel/mgerror.rs
new file mode 100644
index 0000000..453a9bd
--- /dev/null
+++ b/src/kernel/mgerror.rs
@@ -0,0 +1,31 @@
+
+/// Error enum, use it with Result<YourSucessStruct, **ErrorCode**>
+pub enum ErrorCode {
+    INC_ERROR,
+    OPENFILE_ERROR,
+    EXEC_FILE_FORMAT_ERROR,
+    OUT_OF_MEMORY,
+
+    OUT_OF_DISK,
+    ALREADY_IN_DIRECTORY,
+    INEXIST_FILE_ERROR,
+    INEXIST_DIRECTORY_ERROR,
+    NOSPACE_IN_DIRECTORY,
+    NOT_A_FILE,
+    NOT_A_DIRECTORY,
+    DIRECTORY_NOT_EMPTY,
+    INVALID_COUNTER,
+
+    /* Invalid typeId fields: */
+    INVALID_SEMAPHORE_ID,
+    INVALID_LOCK_ID,
+    INVALID_CONDITION_ID,
+    INVALID_FILE_ID,
+    INVALID_THREAD_ID,
+
+    /* Other messages */
+    WRONG_FILE_ENDIANESS,
+    NO_ACIA,
+
+    NUMMSGERROR /* Must always be last */
+}
\ No newline at end of file
diff --git a/src/kernel/mod.rs b/src/kernel/mod.rs
index a5dc06d..135f0a3 100644
--- a/src/kernel/mod.rs
+++ b/src/kernel/mod.rs
@@ -1,3 +1,4 @@
 mod process;
 pub mod thread;
-mod scheduler;
\ No newline at end of file
+pub mod scheduler;
+pub mod mgerror;
\ No newline at end of file
diff --git a/src/kernel/scheduler.rs b/src/kernel/scheduler.rs
index d2670b3..0e71684 100644
--- a/src/kernel/scheduler.rs
+++ b/src/kernel/scheduler.rs
@@ -1,10 +1,12 @@
+use std::sync::Arc;
+
 use crate::utility::list::List;
 use crate::kernel::thread::Thread;
 use crate::utility::system::{G_CURRENT_THREAD, G_THREAD_TO_BE_DESTROYED};
 
 
-struct Scheduler {
-    ready_list: List<Thread>
+pub struct Scheduler {
+    ready_list: List<Arc<Thread>>
 }
 
 impl Scheduler {
@@ -25,8 +27,8 @@ impl Scheduler {
     /// ## Pamameter
     /// 
     /// **thread** is the thread to be put on the read list
-    pub fn ready_to_run(&mut self, thread: Thread) {
-        self.ready_list.push_back(thread);
+    pub fn ready_to_run(&mut self, thread: Arc<Thread>) {
+        self.ready_list.push(thread);
     }
     
     /// Return the next thread to be scheduled onto the CPU.
@@ -35,8 +37,8 @@ impl Scheduler {
     /// Thread is removed from the ready list.
     /// 
     /// **return** Thread thread to be scheduled
-    pub fn find_next_to_run(&mut self) -> Option<Thread> {
-        self.ready_list.pop_back()
+    pub fn find_next_to_run(&mut self) -> Option<Arc<Thread>> {
+        self.ready_list.pop()
     }
 
     /// Dispatch the CPU to next_thread. Save the state of the old thread 
diff --git a/src/kernel/thread.rs b/src/kernel/thread.rs
index a4301f8..7f109df 100644
--- a/src/kernel/thread.rs
+++ b/src/kernel/thread.rs
@@ -1,5 +1,7 @@
-use super::process::Process;
-use crate::{simulator::machine::{NUM_INT_REGS, NUM_FP_REGS, STACK_REG}, utility::system::ObjectType};
+use std::sync::Arc;
+
+use super::{process::Process, mgerror::ErrorCode};
+use crate::{simulator::machine::{NUM_INT_REGS, NUM_FP_REGS, STACK_REG}, utility::system::{ObjectType, G_ALIVE, G_SCHEDULER}, kernel::scheduler};
 
 const SIMULATORSTACKSIZE: usize = 32 * 1024;
 
@@ -43,15 +45,31 @@ impl Thread {
     }
 
     /// Start a thread, attaching it to a process
-    pub fn start(&mut self, owner: Process, func: i64, arg: i64) -> i32 {
+    pub fn start(mut self, owner: Process, func: i64, arg: i64) -> Result<(), ErrorCode> {
         self.process = Option::Some(owner);
         let ptr = 0; // todo addrspace
         self.init_thread_context(func, ptr, arg);
         let base_stack_addr: [i8; SIMULATORSTACKSIZE] = [0; SIMULATORSTACKSIZE]; // todo AllocBoundedArray
         self.init_simulator_context(base_stack_addr);
         self.process.as_mut().unwrap().num_thread += 1;
-        
-        todo!();
+        match G_ALIVE.write() {
+            Ok(mut alive) => {
+                let this = Arc::new(self);
+                alive.push(Arc::clone(&this));
+                match G_SCHEDULER.write() {
+                    Ok(mut scheduler) => {
+                        scheduler.ready_to_run(Arc::clone(&this));
+                    },
+                    Err(err) => {
+                        panic!("RwLock poisonned, {}", err);
+                    }
+                }
+            },
+            Err(err) => {
+                panic!("RwLock poisonned, {}", err);
+            }
+        }
+        Result::Ok(())
     }
 
     fn init_thread_context(&mut self, initial_pc_reg: i64, initial_sp: i64, arg: i64) {
@@ -60,11 +78,24 @@ impl Thread {
         self.thread_context.int_registers[STACK_REG] = initial_sp;
     }
 
-    /// Wait for another thread to finish its execution
-    pub fn join(&self, id_thread: &Thread) {
+    fn init_simulator_context(&self, base_stack_addr: [i8; SIMULATORSTACKSIZE]) {
         todo!();
     }
 
+    /// Wait for another thread to finish its execution
+    pub fn join(&self, id_thread: Arc<Thread>) {
+        match G_ALIVE.write() {
+            Ok(alive) => {
+                while alive.contains(&Arc::clone(&id_thread)) {
+                    self.t_yield();
+                }
+            },
+            Err(err) => {
+                panic!("RwLock poisonned, {}", err)
+            }
+        }
+    }
+
     /// Relinquish the CPU if any other thread is runnable.
     /// 
     /// Cannot use yield as a function name -> reserved name in rust
@@ -87,10 +118,6 @@ impl Thread {
         todo!();
     }
 
-    pub fn init_simulator_context(&self, base_stack_addr: [i8; SIMULATORSTACKSIZE]) {
-        todo!();
-    }
-
     pub fn save_processor_state(&self) {
         todo!();
     }
diff --git a/src/utility/list.rs b/src/utility/list.rs
index 46f5557..a90ec2b 100644
--- a/src/utility/list.rs
+++ b/src/utility/list.rs
@@ -1,178 +1,217 @@
-use std::{cell::RefCell, rc::Rc};
 
-/// Definition of an element of the list
-/// 
-/// Contain one stored item and the previous/next element of the list
-struct ListNode<T> {
-    item: T,
-    next: Link<T>,
-    prev: Link<T>,
-}
-
-impl<T> ListNode<T> {
-    fn new(item: T) -> Self {
-        Self {
-            item,
-            next: None,
-            prev: None,
-        }
-    }
-}
-
-type Link<T> = Option<Rc<RefCell<ListNode<T>>>>;
-
-/// Defintion of the generic linked list
-#[derive(Default)]
-pub struct DoublyLinkedList<T> {
+pub struct List<T: PartialEq> {
     head: Link<T>,
-    tail: Link<T>,
-    size: usize,
 }
 
-impl<T> DoublyLinkedList<T> {
+type Link<T> = Option<Box<Node<T>>>;
 
+struct Node<T> {
+    elem: T,
+    next: Link<T>,
+}
+
+impl<T: PartialEq> List<T> {
     pub fn new() -> Self {
-        Self {
-            head: None,
-            tail: None,
-            size: 0,
-        }
+        List { head: None }
     }
 
-    pub fn is_empty(&self) -> bool {
-        self.len() == 0
+    /// Push an item at the end of the list
+    pub fn push(&mut self, elem: T) {
+        let new_node = Box::new(Node {
+            elem: elem,
+            next: self.head.take(),
+        });
+
+        self.head = Some(new_node);
     }
 
-    pub fn len(&self) -> usize {
-        self.size
-    }
-
-    /// Add the item at the end of the list
-    pub fn push_back(&mut self, item: T) {
-        let node = Rc::new(RefCell::new(ListNode::new(item)));
-        if let Some(prev_tail) = self.tail.take() {
-            prev_tail.borrow_mut().next = Some(Rc::clone(&node));
-            node.borrow_mut().prev = Some(prev_tail);
-            self.tail = Some(node);
-            self.size += 1;
-        } else {
-            self.head = Some(Rc::clone(&node));
-            self.tail = Some(node);
-            self.size = 1;
-        }
-    }
-
-    /// Add the item at the start of the list
-    pub fn push_front(&mut self, item: T) {
-        let node = Rc::new(RefCell::new(ListNode::new(item)));
-        if let Some(prev_head) = self.head.take() {
-            prev_head.borrow_mut().prev = Some(Rc::clone(&node));
-            node.borrow_mut().next = Some(prev_head);
-            self.head = Some(node);
-            self.size += 1;
-        } else {
-            self.head = Some(Rc::clone(&node));
-            self.tail = Some(node);
-            self.size = 1;
-        }
-    }
-    
-    /// Retrieve and remove the item at the end of the list
-    pub fn pop_back(&mut self) -> Option<T> {
-        self.tail.take().map(|prev_tail| {
-            self.size -= 1;
-            match prev_tail.borrow_mut().prev.take() {
-                Some(node) => {
-                    node.borrow_mut().next = None;
-                    self.tail = Some(node);
-                }
-                None => {
-                    self.head.take();
-                }
-            }
-            Rc::try_unwrap(prev_tail).ok().unwrap().into_inner().item
+    /// Retrieve and remove the item at the end of the list.
+    /// 
+    /// Return None if list is empty
+    pub fn pop(&mut self) -> Option<T> {
+        self.head.take().map(|node| {
+            self.head = node.next;
+            node.elem
         })
     }
 
-    /// Retrieve and remove the item at the start of the list
-    pub fn pop_front(&mut self) -> Option<T> {
-        self.head.take().map(|prev_head| {
-            self.size -= 1;
-            match prev_head.borrow_mut().next.take() {
-                Some(node) => {
-                    node.borrow_mut().prev = None;
-                    self.head = Some(node);
-                }
-                None => {
-                    self.tail.take();
-                }
-            }
-            Rc::try_unwrap(prev_head).ok().unwrap().into_inner().item
+    /// Retrieve without removing the item at the end of the list
+    /// 
+    /// Return None if list is empty
+    pub fn peek(&self) -> Option<&T> {
+        self.head.as_ref().map(|node| {
+            &node.elem
         })
     }
-    
+
+    /// Retrieve without removing the item at the end of the list as mutable
+    /// 
+    /// Return None if lsit is empty
+    pub fn peek_mut(&mut self) -> Option<&mut T> {
+        self.head.as_mut().map(|node| {
+            &mut node.elem
+        })
+    }
+
+    /// Search for an element in the list
+    /// 
+    /// Return **bool** true if the list contains the element, false otherwise
+    /// 
+    /// Worst case complexity of this function is O(n)
+    pub fn contains(&self, elem: &T) -> bool {
+        let mut iter = self.iter();
+        let element = iter.next();
+        while element.is_some() {
+            if element.unwrap() == elem {
+                return true;
+            }
+        }
+        false
+    }
+
+    pub fn into_iter(self) -> IntoIter<T> {
+        IntoIter(self)
+    }
+
+    pub fn iter(&self) -> Iter<'_, T> {
+        Iter { next: self.head.as_deref() }
+    }
+
+    pub fn iter_mut(&mut self) -> IterMut<'_, T> {
+        IterMut { next: self.head.as_deref_mut() }
+    }
 }
 
-impl<T> Drop for DoublyLinkedList<T> {
-    /// list destructor, safely desallocate smart pointer Rc
+impl<T: PartialEq> Drop for List<T> {
     fn drop(&mut self) {
-        while let Some(node) = self.head.take() {
-            let _ = node.borrow_mut().prev.take();
-            self.head = node.borrow_mut().next.take();
+        let mut cur_link = self.head.take();
+        while let Some(mut boxed_node) = cur_link {
+            cur_link = boxed_node.next.take();
         }
-        self.tail.take();
     }
 }
 
-impl<T> IntoIterator for DoublyLinkedList<T> {
-    type Item = <ListIterator<T> as Iterator>::Item;
+pub struct IntoIter<T: PartialEq>(List<T>);
 
-    type IntoIter = ListIterator<T>;
-
-    fn into_iter(self) -> Self::IntoIter {
-        Self::IntoIter::new(self)
-    }
-}
-
-pub struct ListIterator<T> {
-    list: DoublyLinkedList<T>,
-}
-
-impl<T> ListIterator<T> {
-    fn new(list: DoublyLinkedList<T>) -> Self {
-        Self { list }
-    }
-}
-
-impl<T> Iterator for ListIterator<T> {
+impl<T: PartialEq> Iterator for IntoIter<T> {
     type Item = T;
+    fn next(&mut self) -> Option<Self::Item> {
+        // access fields of a tuple struct numerically
+        self.0.pop()
+    }
+}
+
+pub struct Iter<'a, T> {
+    next: Option<&'a Node<T>>,
+}
+
+impl<'a, T> Iterator for Iter<'a, T> {
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        self.next.map(|node| {
+            self.next = node.next.as_deref();
+            &node.elem
+        })
+    }
+}
+
+pub struct IterMut<'a, T> {
+    next: Option<&'a mut Node<T>>,
+}
+
+impl<'a, T> Iterator for IterMut<'a, T> {
+    type Item = &'a mut T;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.list.pop_front()
+        self.next.take().map(|node| {
+            self.next = node.next.as_deref_mut();
+            &mut node.elem
+        })
     }
 }
 
-impl<T> DoubleEndedIterator for ListIterator<T> {
-    fn next_back(&mut self) -> Option<Self::Item> {
-        self.list.pop_back()
-    }
-}
-
-pub type List<T> = DoublyLinkedList<T>;
-pub type ListInt = List<i32>;
-
 #[cfg(test)]
 mod test {
-
-    use super::DoublyLinkedList;
+    use super::List;
 
     #[test]
-    fn test_list_push() {
-        let mut list = DoublyLinkedList::new();
-        list.push_back(5);
-        list.push_front(45);
-        assert_eq!(list.pop_front().unwrap(), 45);
-        assert_eq!(list.pop_front().unwrap(), 5);
+    fn basics() {
+        let mut list = List::new();
+
+        // Check empty list behaves right
+        assert_eq!(list.pop(), None);
+
+        // Populate list
+        list.push(1);
+        list.push(2);
+        list.push(3);
+
+        // Check normal removal
+        assert_eq!(list.pop(), Some(3));
+        assert_eq!(list.pop(), Some(2));
+
+        // Push some more just to make sure nothing's corrupted
+        list.push(4);
+        list.push(5);
+
+        // Check normal removal
+        assert_eq!(list.pop(), Some(5));
+        assert_eq!(list.pop(), Some(4));
+
+        // Check exhaustion
+        assert_eq!(list.pop(), Some(1));
+        assert_eq!(list.pop(), None);
     }
 
+    #[test]
+    fn peek() {
+        let mut list = List::new();
+        assert_eq!(list.peek(), None);
+        assert_eq!(list.peek_mut(), None);
+        list.push(1); list.push(2); list.push(3);
+
+        assert_eq!(list.peek(), Some(&3));
+        assert_eq!(list.peek_mut(), Some(&mut 3));
+
+        list.peek_mut().map(|value| {
+            *value = 42
+        });
+
+        assert_eq!(list.peek(), Some(&42));
+        assert_eq!(list.pop(), Some(42));
+    }
+
+    #[test]
+    fn into_iter() {
+        let mut list = List::new();
+        list.push(1); list.push(2); list.push(3);
+
+        let mut iter = list.into_iter();
+        assert_eq!(iter.next(), Some(3));
+        assert_eq!(iter.next(), Some(2));
+        assert_eq!(iter.next(), Some(1));
+        assert_eq!(iter.next(), None);
+    }
+
+    #[test]
+    fn iter() {
+        let mut list = List::new();
+        list.push(1); list.push(2); list.push(3);
+
+        let mut iter = list.iter();
+        assert_eq!(iter.next(), Some(&3));
+        assert_eq!(iter.next(), Some(&2));
+        assert_eq!(iter.next(), Some(&1));
+    }
+
+    #[test]
+    fn iter_mut() {
+        let mut list = List::new();
+        list.push(1); list.push(2); list.push(3);
+
+        let mut iter = list.iter_mut();
+        assert_eq!(iter.next(), Some(&mut 3));
+        assert_eq!(iter.next(), Some(&mut 2));
+        assert_eq!(iter.next(), Some(&mut 1));
+    }
 }
\ No newline at end of file
diff --git a/src/utility/system.rs b/src/utility/system.rs
index 701e0b7..08dc9bf 100644
--- a/src/utility/system.rs
+++ b/src/utility/system.rs
@@ -1,8 +1,8 @@
-use std::sync::{RwLock, Arc};
+use std::{sync::{RwLock, Arc}};
 
 use lazy_static::lazy_static;
 
-use crate::kernel::thread::Thread;
+use crate::kernel::{thread::Thread, scheduler::Scheduler};
 
 use super::list::List;
 extern crate lazy_static;
@@ -10,7 +10,8 @@ extern crate lazy_static;
 lazy_static! {
     pub static ref G_CURRENT_THREAD: RwLock<Option<Thread>> = RwLock::new(Option::None);
     pub static ref G_THREAD_TO_BE_DESTROYED: RwLock<Option<Thread>> = RwLock::new(Option::None);
-    // pub static ref G_ALIVE: Arc<RwLock<List<Thread>>> = Arc::new(RwLock::new(List::new()));
+    pub static ref G_ALIVE: RwLock<List<Arc<Thread>>> = RwLock::new(List::new());
+    pub static ref G_SCHEDULER: RwLock<Scheduler> = RwLock::new(Scheduler::new());
 }